I would verify that the choke is working properly. Would add some fuel line drier like Heet or another brand to the fuel and drain a little fuel out of the carb, and try it again. Certainly a new genuine and not counterfeit spark plug may help. If that fails, I would definitely adjust the valves to be sure they are still in spec. They expand as they heat up so if one or more is tight, heat can cause it to expand to where an engine runs poorly or dies. Also would use the original carb after checking the bowl for corrosion since the replacement did not help. While the valves are being adjusted, retorque the heads in case they are loose and losing compression. If that helps then prepare to pull them when you have time, check for warp and address as needed. When you put the old carb back on, let a little fuel flow into a glass jar - maybe 1/2 inch and see what it looks like. Also pay attention to how fast it flows. If your engine has a fuel pump, they wear out too and that can cause problems.